1. Field of the Invention
In the processing of petroleum distillates and other hydrocarbonaceous feeds, the presence of paraffins is often undesirable. For example, when a distillate is hydrocracked, the paraffins will be cracked in significant and undesirable amounts to light paraffinic gases, which are usually burned or used as LPG fuels and which are not useful for further processing.
Because losses to relatively low profit gases are significant, there is a continuing search for methods of dewaxing petroleum distillates by processes yielding chemical products which are amenable to further processing to more profitable products.
We have discovered that under certain processing conditions, ZSM-5-type zeolites can be used to dewax, or to remove paraffins, from petroleum and other hydrocarbonaceous feedstocks by forming C.sub.3 -C.sub.4 olefins which are valuable chemicals amenable to further processing steps. Further, the residual uncracked material has improved characteristics useful for reforming operations to make gasoline.
These benefits are achieved through a process which uses a ZSM-5-type catalyst in a matrix substantially free of hydrocarbon cracking activity and a low nitrogen feedstock. Additionally, the process of this invention is particularly useful because the coking and deactivation rate of the catalyst composite is exceptionally low leading to greater efficiency in refinery operations. Further, the process can be practiced at any stage of hydrocarbon processing where it is desired to remove normal or slightly branched paraffins without detrimentally affecting the other chemical components of a feed.
We have also discovered that gas oil range feedstocks can be used more efficiently in making jet fuel. Higher end point jet fuel is produced. The jet fuel has good freeze and smoke points and is produced in high yield.